refactor(gemini-web): Move provider logic to its own package

The Gemini Web API client logic has been relocated from `internal/client/gemini-web` to a new, more specific `internal/provider/gemini-web` package. This refactoring improves code organization and modularity by better isolating provider-specific implementations.

As a result of this move, the `GeminiWebState` struct and its methods have been exported (capitalized) to make them accessible from the executor. All call sites have been updated to use the new package path and the exported identifiers.

internal/provider/gemini-web/prompt.go

@@ -0,0 +1,130 @@
+package geminiwebapi
+
+import (
+	"math"
+	"regexp"
+	"strings"
+	"unicode/utf8"
+
+	"github.com/tidwall/gjson"
+)
+
+var (
+	reThink     = regexp.MustCompile(`(?s)^\s*<think>.*?</think>\s*`)
+	reXMLAnyTag = regexp.MustCompile(`(?s)<\s*[^>]+>`)
+)
+
+// NormalizeRole converts a role to a standard format (lowercase, 'model' -> 'assistant').
+func NormalizeRole(role string) string {
+	r := strings.ToLower(role)
+	if r == "model" {
+		return "assistant"
+	}
+	return r
+}
+
+// NeedRoleTags checks if a list of messages requires role tags.
+func NeedRoleTags(msgs []RoleText) bool {
+	for _, m := range msgs {
+		if strings.ToLower(m.Role) != "user" {
+			return true
+		}
+	}
+	return false
+}
+
+// AddRoleTag wraps content with a role tag.
+func AddRoleTag(role, content string, unclose bool) string {
+	if role == "" {
+		role = "user"
+	}
+	if unclose {
+		return "<|im_start|>" + role + "\n" + content
+	}
+	return "<|im_start|>" + role + "\n" + content + "\n<|im_end|>"
+}
+
+// BuildPrompt constructs the final prompt from a list of messages.
+func BuildPrompt(msgs []RoleText, tagged bool, appendAssistant bool) string {
+	if len(msgs) == 0 {
+		if tagged && appendAssistant {
+			return AddRoleTag("assistant", "", true)
+		}
+		return ""
+	}
+	if !tagged {
+		var sb strings.Builder
+		for i, m := range msgs {
+			if i > 0 {
+				sb.WriteString("\n")
+			}
+			sb.WriteString(m.Text)
+		}
+		return sb.String()
+	}
+	var sb strings.Builder
+	for _, m := range msgs {
+		sb.WriteString(AddRoleTag(m.Role, m.Text, false))
+		sb.WriteString("\n")
+	}
+	if appendAssistant {
+		sb.WriteString(AddRoleTag("assistant", "", true))
+	}
+	return strings.TrimSpace(sb.String())
+}
+
+// RemoveThinkTags strips <think>...</think> blocks from a string.
+func RemoveThinkTags(s string) string {
+	return strings.TrimSpace(reThink.ReplaceAllString(s, ""))
+}
+
+// SanitizeAssistantMessages removes think tags from assistant messages.
+func SanitizeAssistantMessages(msgs []RoleText) []RoleText {
+	out := make([]RoleText, 0, len(msgs))
+	for _, m := range msgs {
+		if strings.ToLower(m.Role) == "assistant" {
+			out = append(out, RoleText{Role: m.Role, Text: RemoveThinkTags(m.Text)})
+		} else {
+			out = append(out, m)
+		}
+	}
+	return out
+}
+
+// AppendXMLWrapHintIfNeeded appends an XML wrap hint to messages containing XML-like blocks.
+func AppendXMLWrapHintIfNeeded(msgs []RoleText, disable bool) []RoleText {
+	if disable {
+		return msgs
+	}
+	const xmlWrapHint = "\nFor any xml block, e.g. tool call, always wrap it with: \n`````xml\n...\n`````\n"
+	out := make([]RoleText, 0, len(msgs))
+	for _, m := range msgs {
+		t := m.Text
+		if reXMLAnyTag.MatchString(t) {
+			t = t + xmlWrapHint
+		}
+		out = append(out, RoleText{Role: m.Role, Text: t})
+	}
+	return out
+}
+
+// EstimateTotalTokensFromRawJSON estimates token count by summing text parts.
+func EstimateTotalTokensFromRawJSON(rawJSON []byte) int {
+	totalChars := 0
+	contents := gjson.GetBytes(rawJSON, "contents")
+	if contents.Exists() {
+		contents.ForEach(func(_, content gjson.Result) bool {
+			content.Get("parts").ForEach(func(_, part gjson.Result) bool {
+				if t := part.Get("text"); t.Exists() {
+					totalChars += utf8.RuneCountInString(t.String())
+				}
+				return true
+			})
+			return true
+		})
+	}
+	if totalChars <= 0 {
+		return 0
+	}
+	return int(math.Ceil(float64(totalChars) / 4.0))
+}